System for monitoring remotely related buildings

ABSTRACT

A system for accommodating a simultaneous monitoring of the integrity of a plurality of remotely related buildings from a common observation station, characterized by a plurality of monitoring units each having an integrity monitoring circuit, integrated with one of a plurality of said remotely related buildings for continuously conducting an electrical current, the amperage of which is indicative of building integrity, and an observation circuit located at the observation station common to all monitoring units remotely related to the buildings including circuit means responsive to changes in said amperages for providing intelligence indicative of a changed status of building integrity.

United States Patent [191 Worsley, Jr. et al.

111 3,823,391 July 9,1974

[ SYSTEM FOR MONITORING REMOTELY RELATED BUILDINGS [75] Inventors: PaulR. Worsley, Jr.; Jerry D.

Baker, both of Fresno, Calif.

[73] Assignee: Valley Burglar & Fire Alarm Company 22 Filed: Jan. 22,1973 21 Appl. No.: 325,631

[52] US. Cl 340/213 R, 340/253 11, 340/276,

12/1969 McGrath 340/213 10/1972 Lee 340/276 Primary Examiner-John W.Caldwell Assistant Examiner-Richard P. Lange Attorney, Agent, orFirm-Huebner & Worrel [57] ABSTRACT A system for accommodating asimultaneous monitoring of the integrity of a plurality of remotelyrelated buildings from a common observation station, characterized by aplurality of monitoring units each having 1 an integrity monitoringcircuit, integrated with one of a plurality of said remotely relatedbuildings for continuously conducting an electrical current, theamperage of which is indicative of building integrity, and anobservation circuit located at the observation station common to allmonitoring units remotely related to the buildings including circuitmeans responsive to changes in said amperages for providing intelligenceindicative of a changed status of building integrity.

11 Claims, 3 Drawing Figures OBSERVATION g STATION 4 I at /a Ls 5 r i t*1 L 3 If 1 5 6 I SYSTEM FOR MONITORING REMOTELY RELATED BUHJDINGSBACKGROUND OF THE INVENTION The invention relates to a system forsimultaneously monitoring the integrity of a plurality of remotelyrelated buildings, and more particularly to a system for use insimultaneously monitoring the integrity of remotely related buildings,with respect to intrusion, em-

ploying telephone or hard lines connecting a plurality of monitoringcircuits located in mutually remote buildings with a plurality ofobservation circuits located at a common observation station, which is,in turn, remotely related to the buildings.

Burglar alarms are notoriously old and are commonly employed fordetecting unauthorized intrusion of protected premises. Among suchsystems are'the so-called silent alarms, including closed circuit T.V.monitoring systems, employed in monitoring the integrity of a selectedbuilding. Such systems are responsive to an intrusion for providing awarning signal at a remote observation station. Where a T.V. monitoringsystem is employed a video signal is provided.

Often times, systems of the type heretofore employed are readily subjectto being defeated orv rendered ineffective through various techniques,such as crossshorting circuit components, generation of false signals,and even circuit interruption, whereby breaking and entering a thusprotected premises can be achieved undetected.

Furthermore, systems heretofore employed often are capable offunctioning in only a single mode, and therefore cannot readily undergoa change in modes for accommodating alternate day and night operations.For example, during daylight hours, it maybe desirable to protect onlyskylights, rear doors, and the like, while at night additional areas ofthe building must be monitored and thus protected against unauthorizedintrusion. Accordingly, monitoring circuits heretofore employed havebeen duplicated in those instances where dual monitoring functions arerequired.

It, therefore, is the purpose of the instant invention to provide ahighly dependable, efficient, economic and practical monitoring systemfor use in simultaneously monitoring the integrity of a plurality ofremotely related buildings from a common observation station, duringboth day and night operations.

OBJECTS AND SUMMARY OF THE INVENTION It therefore is an object of theinstant invention to provide an improved system for monitoring theintegrity of remotely related buildings from a common observationstation.

It is another object to provide a simplified, economic, and practicalsystem for simultaneously monitoring the integrity of a plurality ofremotely related buildings, the mode of which can selectively be alteredfor accommodating day and night operations, and is not subject to beingdefeated through a use of circuit interruption and/or cross shortingtechniques. a

It is another object to provide a simplified, economic, and practicalmonitoring circuit for continuously monitoring the integrity of remotelyrelate buildings from a common observation station employing color codedlights for indicating circuit condition and status change.

These and other objects and advantages are achieved through the use of asystem which iincludes a plurality of remotely related, integritymonitoring circuits, each being disposed within one of a plurality ofselected buildings, including circuit means for continuously conductingan electrical current, the amperage of which is indicative of buildingintegrity, and a plurality of observation circuits located at a commonobservation station and connected with said plurality of monitoringcircuits through hard line circuitry, having means responsive to changesin current amperages flowing through the monitoring circuits forcontinuously providing intelligence indicative of the status ofintegrity for each of the buildings, as will become more readilyapparent by reference to the following description and claims in lightof the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view of asystem which embodies the principles of the instant invention, depictinga plurality of monitoring units including monitoring circuits coupledwith observation circuits located at a common observation station.

FIG. 2 is a schematic view of a combined monitoring circuit and anobservation circuit electrically coupled into a monitoring unit andemployed by the system shown in FIG. 1.

.FIG. 3 is a schematic view, in diagram form, more clearly illustratingthe observation circuit depicted in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more specificallyto the drawings wherein like reference characters designate like orcorresponding parts throughout the several views, there is shown in FIG.I a system, generally designated I0, which embodies the principles ofthe instant invention.

The system 10, as employed, includes an observation station, generallydesignated 12, and a plurality of re motely related integrity monitoringcircuits, generally designated 14.

The observation station 12 is, in practice, located within a fireproofbuilding, or blockhouse, and secured with respect to unauthorizedintrusion. Within the blockhouse there is provided a suitable consolefor simultaneously receiving and supporting a multiplicity of circuitboards, not shown. Each of the circuit boards, as a practical matter,includes a single observation circuit 16 mounted thereon. The circuit I6is fabricated employing techniques fully understood by those familiarwith a fabrication of printed circuits and a use of solid-state devices.

From each observation circuit there is extended a suitable lead whichis, in effect, a continuation of a hard line 18, such as a telephoneline, employed in coupling the observation circuit with one. of theintegrity monitoring circuits to thus form a monitoring unit, designated19.

Each of the integrity monitoring circuits 14 is located within aselected building, the integrity of which is to be monitored. As apractical matter, the primary function of the system 10 is to determinethe instant that any one of a multiplicity of buildings is subjected tounauthorized intrusion. Consequently, the term integrity .components 20and 22. As a practical matter, the circuit 14 includes leads of copperwires, printed circuits, appropriate switches and the like which extendas a monitoring network throughout the building and located to bebroken, activated and the like in response to unauthorized intrusion.

Since monitoring circuits are well known, a detailed description of thespecific monitoring circuit employed is omitted in the interest ofbrevity. However, it is to be understood that the monitoring circuit iscontinuously conductive and in the event the monitoring circuit isinterrupted, or cross-shorted, the resistance of the circuit is varied,whereupon the amperage of the flow of electrical current is varied.Furthermore, the system is coupled at the negative terminal of a 24 voltd.c. source of-electrical potential 23. The positive terminal of thesource is connected to ground. Consequently, the system 10 employsso-called single-line circuitry with current flow being directed througheach of the observation circuits l6, thence to ground through a hardline 18 and an integrity monitoring circuit 14 for thus completing thecircuit through the unit 19.

Each of the variable resistances 20 and 22, illustrated in FIG. 2, isrepresentative of a single portion of the integrity monitoring circuit14, which is, in operation, employed alternatively for accommodating dayand night operations. Consequently, the variable resistance 20 isintended to represent a portion of the circuit 14 employed when thecircuit is switched to its normal day mode or during normal operationsconducted during daylight hours, while the variable resistance 22 isintended to depict a portion of the circuit employed when the circuit isswitched to normal night mode or during operation conducted at night. Ofcourse, the operation of theportion of the circuits designated 20 and 22are in no way dictated by hours or by daylight conditions, and thus itcan be appreciated that the phrases normal day and normal night modesare employed as a matter of convenience in distinguishing betweenperiods when selected circuit portions are employed.

In order to accommodate a switching between the portions of the circuitsrepresented by the variable resistances 20 and 22, there is provided amanually operable switch 24. In practice, this switch is manipulated bypersonnel within a building for purposes of switching the operation ofthe system 10 for operation in normal day and normal night modes.

As will hereinafter become more fully apparent, th observation circuit16 monitors the status of the circuit 14 and thus provides intelligenceindicative of changes occurring in the status. Consequently, it isimprobable if not impossible for an intruder to defeat the system 10 byswitching the circuit between its modes of operation, since each timethe mode is changed intelligence indicative of the change is presentedby the observation circuit 16 to personnel within the observationstation 14.

It is to be understood that each circuit unit 19 includes a monitoringcircuit 14 and an observation circuit 16. Since the units 19 can beadded and deleted without interrupting the function of the remainingportions of the system 10 and the design and construction of the units19 are quite similar, a detailed description of a single unit isbelieved adequate for providing a complete understanding of the instantinvention.

Referring now to FIGS. 2 and 3, it is noted that the circuit 16 iscoupled with the hard lines 18 at a circuit switch S1, within a block,designated A. This switch is employed for coupling a ring-back circuit26 with the hard line 18 employed in coupling the circuits 14 and 16.The purpose of the ring-back circuit 26 is to impose a volt signal onthe line 18 so that personnel within a building being monitored by acircuit 14 is provided with a signaling voltage which indicates that theintegrity of the line 18 and thee circuit 14 are in tact. Normally, thisis performed in the blockhouse, or at the observation station 12 at thetime the building is closed.

As a practical matter, it is important to note that circuit 16 includesa lead 29 which serves to conduct current from the source 23 to thecircuit while a lead 30 is provided for coupling the circuit withground. Electrically connected between the leads 29 and 30 is an RFfilter circuit, designated by block B, FIG. 2, which includes a 100,000ohm resistor 31 and a 0.22 microfarad capacitor 32. Accordingly, thecircuit of the unit 19 is protected against an introduction of highvoltage RF signal.

Switch S1, FIG. 2, is electrically connected with a circuit block C. Asa practical matter, block C includes a current limiting and transientfilter circuit through which high voltage transient signals are clippedwhereby the circuit 16 is protected from excessive current loads. As apractical matter, block C includes a 6.4 kilohm resistor 28, connectedin series with the switch S1, employed in limiting current flow throughthe circuitry for thereby affording a degree of protection thereto.

Block C also functions in a protective and transient filter function.This circuit, as best shown in FIG. 3, is a parallel circuit having thevoltage from the source 23 applied thereto, through the lead 29, andincludes a 5.6 volt Zener diode 34 provided for clipping high voltagetransient signals to that level, as well as a pair of 0.22 microfaradcapacitor 36. The capacitors serve to filter pulse signals of RFfrequency as well as pulse signals of relatively long pulse durations.

Immediately following block C, as illustrated in FIG. 2, are blocks D,E, F and G, which collectively serve to detect changes in the conditionof the circuit of the unit 19. In practice, the circuit of block Dincludes an electrically energizable lamp 44, preferably yellow, thecircuit of block E includes an electrically energizable lamp 46,preferably green, the circuit of the block F includes electricallyenergizable lamp 48, preferably white, while the circuit of block Gincludes an electrically energizable lamp 50, preferably red.

The lamps 44, 46, 48 and 50 have one terminal connected to groundthrough a switch S2 and are energized for indicating a condition of thecircuit of the unit 19. Such an indication serves as intelligencerelated to the integrity of the building being monitored. Each of thecircuits of blocks D, E, F and G, in turn, are coupled with astatus-change block, designated H, through leads 52, 54, 56 and 58,respectively. Within the circuit of the block H there is includedanother electrically energizable lamp 60, preferably blue in color. Thislamp is energized upon a change in the amperage of the cur rent flowingthrough the unit 19.

Accordingly, it should be apparent that the blocks D, E, F and G serveas current detection stages and detect current changes for the currentflowing through the unit 19. In practice, the blocks D, E, F and G arecon nected through a common lead 62 with the current limiting andtransient signal filter circuit of block C. Thus, a current path isprovided simultaneously to all of the blocks D, E, F, and G from thecircuit 14.

Each of the current detection stages, or blocks D, E, F and G, isprovided with a signal pick-off circuit, generally designated 64. Eachof the pick-off circuits, in turn, includes a lead 66 through which apotentiometer 68 is connected with the lead 29, FIG. 3. Each of thepotentiometers is provided with a wiper arm 70 and a resistor 72relative to which the wiper arm 70 is adjustable. For reasons wellunderstood, the current delivered through the wiper arm 70 can be variedsimply by repositioning the wiper arm relative to the resistor.

Each of the wiper arms 70 is, in turn, coupled electrically to the baseof an NPN transistor 74, all being similarly biased. As a practicalmatter, the transistors employed are of the type designated 2N2923, eachhaving a negative voltage applied to its emitter while ground potentialis applied to its collector. As a practical matter, current limitingresistors 76 are interposed between the wiper arms 70 and the base ofthe transistors 74, of blocks D, E and F for adjustment and protectivepurposes.

The collectors of the transistors 74, within the circuits of blocks D, Eand F are connected to ground through kilohm resistors 78, while theemitters thereof are connected directly with the -24 volt d.c. source ofpotential, through leads 80 electrically connected with the lead 29.

It should therefore be readily apparent that each of the transistors 74is forward biased by a voltage pickedoff by an arm 70 and applied to thebase thereof. However, once the current established through the resistor76 drops to a preselected level, the biasing voltage applied to the baseof the transistors 74 is removed whereupon the transistor ceases toconduct between the source 23 of electrical potential and ground. Thus,the circuits 64, in effect, continuously monitor the current flowingthrough the circuit 14 and are responsive to voltage signals of selectedvalues applied to the bases of the NPN transistors 74.

Turning now to the first current detecting stage or circuit of block C,FIG. 3, it is noted that the lamp 44 also is connected with the negativedc. voltage through an SCR 82. The SCR is configured to be fired by agatinng signal, at ground potential, directed through a directionaldiode 84 and applied to its gate. False triggering of the SCR diode 82is prevented by a filter circuit, generally designated 86, whiichincludes a one kilohm resistor 88 and a 0.22 microfarad capacitor 90.The circuit of block D is set to respond to a current of 0.75 ma(milliampere) or less flowing through hard lines 18. As a practicalmatter, this current is no more than carrying current for the phoneline. Accordingly, this circuit functions in the event the circuit 14 isopened by an intruder.

Once the voltage of the signal applied to the base of the transistor 74is dropped to a selected low level, the transistor 74 is switched-off,i.e. ceases to conduct.

Therefore, a gating signal is applied from ground to the gate of the SCRdiode 82 causing that diode to fire. Thereupon a circuit is completedthrough the lamp 44, between ground and the source of negative potentialso that the lamp 44 thus is energized. Enerization of the lamp 44, ofcourse, indicates that a current through the circuit 14 is reduced to alevel indicating that an open condition for the circuit 14 exists. Thisindication serves as intelligence warning of the presence of an intruderwithin the building being monitored.

The circuit of block E is quite similar to that of block D and isemployed for indicating that the circuit 114 is set in a normal nightmode, indicated through the ener gization of the lamp 46, preferablygreen in color. This circuit includes an NPN transistor 92, the base ofwhich is connected with the collector of the NPN transistor 74 throughdirectional diode 94. The collector of the transistor 92 is connected toground thorugh a 10 kilohm resistor 96, while the emitter is connectedto the source of negative voltage through ohm resistor 98.

The lamp 46, as before mentioned, has one terminal thereof connected toground through the switch S2, while the other is connected to the sourceof negative voltage through still another NPN transistor 100. Theemitter of the transistor 100 is connected to the source of negativevoltage 23, also via the resistor 98. The base of the transistor 100 isconnected between the collector of the transistor 92 and the resistor 96through a directional diode 102. In practice, the potentiometer 68 ofthe pick-off circuit 64 within the circuit of block E is so set thatwhen the circuit l4 is switched to its normal night mode a current of0.8 ma. to l.l5 ma. is present through the resistance 72. This causes aforward biasing voltage to be applied to the base of the transistor 74so that it is switched on or rendered conductive. Once the transistor 74is switched on, ground potential is removed from the base of thetransistor 92 causing it to switch off. Once the transistor 92 isswitched off, ground potential is applied to the base of transistor 100for thereby switching it on. Hence, once the transistor 74 of thepick-off circuit 64 is switched on by switching the circuit 14 to itsnormal night mode, the transistor 92 is rendered non-conductive so thatground potential is applied through resistance 96 and the diode 102 forswitching the transistor 100 on. As the transistor 100 begins toconduct, this heavier current causes the voltage drop across theresistance 98 to increase. This voltage drop serves to reverse bias thetransistor 92 further aiding in the connduction of the transistor 100.As a practical matter, this results in speeding the switching of thetransistor 100 so that the lamp 46 is rapidly switched on once thetransistor 74 is switched on.

Thus, it is readily apparent that when the circuit 14 is set in itsnormal night mode, th green light 46 remains energized so that personnelwithin the observation station 12 are continuously aware of thecondition of the unit 19.

Turning now to the third current detecting circuit of block F, it shouldreadily be apparent that this circuit is substantially the same as thecircuit of block E. However, it also is important to note that thecircuit of block F includes an NPN transistor 104, the base of which isconnected between the collector of the transistor 74 of the pick-offcircuit 64 and ground potential through a directional diode 106. Thecollector of the transistor 104 is connected to ground through a 15kilohm resistor 108 and the emitter thereof is connected to the negativepotential through a 100 ohm resistor 110.

An NPN transistor 112 is connected at its collector with one terminal ofthe non-grounded terminal of the lamp 48 while the emitter thereof alsois connected with negative potential through the resistor 110. The baseof the transistor 1 12 is connected between the collector of thetransistor 104 and the resistor 108 through a diode 114. This circuitserves to provide intelligence indicative of the normal day modeoperation an operates in substantially the same manner as the circuit ofthe second current detecting stage of block E. However, it is importantto note here that when the threshold voltage, established by theadjustment of the potentiometer 68 of the pick-off circuit 64, isreached the current flow attains a value of 1.15 ma. Thus,. when thevoltage attendant 1.15 to 1.40 ma, as seen through the potentiometer 64,is applied to the base of the transistor 74, the lamp 48 is energized asthe transistor 112 is switched on as a result of a biasing signal beingdelivered to the base thereof through a diode 1114.

It is important to herenote that a PNP transistor 115 is coupled at itscollector with the base of the NPN transistor 92 while the emitterthereof is connected to ground potential. The base of the PNP transistoris connected with ground and with the non-grounded terminal of the lamp48 through a suitable biasing resistor network, not designated. Once acurrent path is established through the lamp 48, the transistor 115 ispermitted to switch on, whereupon transistor 92 becomes forward biasedand transistor 100 is thus maintained in a reverse biased condition forthus assuring that the lamp 46 remains de-energized so long as the lamp48 is energized.

Turning now to the circuit off block G, it is noted that the lamp 50 isconnected with the negative voltage source 23 through an SCR 116 whichis switched on in response to a gating signal applied to the gatethereof when the current through the pick-off circuit 64 attains a level1 of 1.4 ma., normally experienced at any time a cross-short occurs. Thegating signal is derived from the emitter of the NPN transistor 74through a current limiting resistor 120 connected thereto. Thetransistor 74 is connected to ground at its collector, through 4.7kilohm resistor 122, while the emitter thereof is connected to the lead29 through a 1 kilohm resistor 124. A filtering circuit 126 is connectedbetween the input to the gate of the SCR 116 an the lead 29 forpreventing an application of false signals to the gate of the SCR 116.The filter circuit 126 includes 0.22 microfarad capacitor 128 and 1kilohm resistor 130 arranged in circuit parallel.

Consequently, once the current through the potentiometer 68 of thepick-off circuit 64 reaches the level of 1.4 ma., the transistor 74 ofthe pick-off circuit 64 is caused to conduct in response to the voltagelevel of the signal applied to the base thereof through a wiper arm 70.As the transistor 74 conducts, the gating signal is delivered, via theresistor 120, to the gate of the SCR 116 whereupon a current path isestablished through the lamp 50, between its grounded terminal and thesource 23, whereupon the lamp 511 is energized. Since the lamp 50propagates light of the color red, once current flow through the circuit14 reaches a high level indicating a cross short. Thus, an observer atthe observation station 12 is provided with intelligence indicative ofthe cross-short condition for the circuit 14. Such a condition normallyindicates an interruption of building integrity caused throughintrusion.

It is important to appreciate that monitoring personnel at theobservation station 12 should be apprised of prior changes in circuitcondition, even though such personnel were not aware of such a change atthe instant it occurred. To achieve this there is provided astatus-change circuit stage, block H, which responds to each change inthe condition of the circuit and provides intelligence in the form oflight of a blue color emanating from lamp 611 which is connected betweenground and the negative voltage source 23 through SCR 134. A gatingsignal for the SCR 134 is derived through a PNP transistor 136, thecollector of which is connected with the lead 29 through a 15 kilohmresistor 138 while the emitter thereof is connected to ground. The baseof the transistor 136 is biased to a non-conducting mode through aresistor 140 connected between the base and ground potential. Thus, theresistor 136 normally is biased to its non-conducting state.

Also coupled to the base of the transistor 136 is a plurality ofdetection leads 142, 144, 146 and 148 which extend from connectionsestablished between the voltage source 23 and each of the lamps 44, 46,48 and 50, respectively. Accordingly, it is to be understood that once acurrent flow is established through any of the lamps 44 through 50, theleads 142 through 148 serve to apply a negative voltage to the base ofthe transistor 136 for switching this transistor to its conductingstate, by overcoming the biasing signal applied to the base through theresistor 140.

As a practical matter, each of the leads 142 through 148 includestherein, in series, a 2.2 microfarad capacitor 149 and a 1 kilohmresistor 149R so that the nega tive signal derived through theconnection of the leads with the lamps 44 through 50 applies a switchingsignal to the base of the resistor 136 for a period determined by thetime constant of the capacitor 149 and the series connected resistor149R. As a practical matter, a filter circuit 150, which includes a 1kilohm resistor 152 and a 0.22 microfarad capacitor 154, is provided forpreventing a firing of the SCR 134 through an application of a falsesignal.

It should, therefore, be apparent that once the transistor 136 is causedto conduct in response to a nega' tive signal applied to its base, agating signal is applied to the SCR 134, whereupon the current pathbetween ground the the source 23, through the lamp 60, is establishedfor energizing the lamp to provide light of a blue color. This lamp thusserves to indicate that a change in circuit conditions has beenexperienced.

ln addition to energizing the lamp 60 an audible signal generator 156 isconnected with the circuit 116 at pin P. Pin P, in turn, is connectedbetween the SCR 134 and the lamp 60 so that when the SCR 134 is causedto conduct a negative voltage is applied to the pin. This signal is thenapplied to the signal generator so that an audible signal, as well as avisual signal, is provided at each change in a set condition which isindicative of a change which has occurred in the integrity of thebuilding being monitored by the circuit 14. As a practical matter, acurrent limiting resistor 158 is interposed between the SCR 134 and thepin P.

Of course, once intelligence has been provided at the observationstation 12, circuit monitoring personnel must be afforded an opportunityto reset the circuit of the unit 19. This is achieved through the resetswitch S2 which, through an NPN transistor 160 interrupts flow ofcurrent through the lamp 60 and to the audible Signal generator 156. I

In practice, the emitter of the NPN transistor 160 is coupled with thenegative voltage source 23, through the lead 29, while the collectorthereof is connected between the lamp 60 and the SCR 134. Accordingly, acurrent path established through the transistor 160 causes a current tobypass the SCR 134, permitting the SCR to reset to its non-conductingstate. As a practical matter, a pair of directional diodes 162 areconnected in series between the SCR 134 and the collector of the NPNtransistor 160 in order to assure that the SCR 134 is afforded anopportunity to reset in the presence of the transistor 160 in itsconductive state.

Normally, the transistor 160 is biased to a nonconductive state througha 10 microfarad capacitor 164 and a'current limiting resistor 166.HoweverQit is noted that the resistor 166 also is connected through adirectional diode 168 and a current limiting resistor 170 to a pole,designated 172, of the switch S2. It is to be understood that the switchS2 is a single pole double-throw switch normally open between the pole172 and ground, while being closed between the lamps 44, 46, 48 and 50and ground. However, in order to reset the circuit and thus clearintelligence from the observation circuit 116, the switch S2 ismanipulated so that the circuit is opened between the lamps 44 through50 and ground while a circuit is completed from ground to the base ofthe transistor 160 via resistors 166 and 170. Of course, a completion ofthe circuit between the pole 172 and ground causes ground potential tobe applied to the base of the transistor 160 for overcoming the negativebias of the capacitor 164. Of course, the capacitor 164 is permitted tocharge through a directional diode 174. The pin P also is connected withthe pole 172, through the resistor 170 and a directional diode 176.Accordingly, ground potential is applied between the resistor 158 andthe pin for removing the negative voltage applied thereto through thetransistor 160 as the pole 172 of the switch S2 is grounded. As apractical matter, a directional diode 178 is interposed between the pinand the collector of the transistor 160 in order to prevent a negativevoltage from being applied to the collector from the pin.

Accordingly, it should be appreciated that once the switch S2 ismanipulated so that the circuit between the lamps 44 through 50 andground is interrupted, while the circuit between the base of thetransistor 16,0 and ground is completed, the SCRs 82, 116 and 134 aswell as NPN transistors 100 and 112 are switched to a nonconducting modefor resetting the circuit and turning off the audible signal generator.Of course, once the circuit is interrupted between the pole 172 andground, by returning the switch S2 to its normal condition, groundpotential is again applied to each'of the lamps by' the switch S2.

In practice, the capacitor 164, upon an opening of the circuit at theswitch S2 between the pole 172 and ground discharges for a period of onesecond for biasing the SCR 134 to an off condition through thetransistor 160. The circuit is now prepared for reactivation inaccordance with its normal mode of operation.

OPERATION It is believed that in view of theforegoing description, theoperation of the system will be readily understood and it will bebriefly reviewed at this point.

With the circuit fabricated in the aforedescribed configuration,intelligence is provided at the observation 1 station 12 in accordancewith the color of light emanating from the circuit lamps 44 through 60.This intelligence is depicted as follows:

The unit 19 is particularly suited for use where the opening and closingtimes of buildings to be monitored are known by monitoring personnel atthe observation station, since the precise operation requires that thepremises be opened and closed within a minimal time period. The open orclosed, that is the night or day modes for the unit, are indicated bythe green and white lights and are set by a manipulation of the switch24 at the premises. A change between green and white lamps indicates themanipulation of the switch 24, while an energization of the red andyellow lamps 44 and 50 indicate intrusion in the building. Of course,any change in the condition of the circuit is indicated by anenergization of the blue lamp and a tone derived from the audible signalgenerator 156. By manipulating the switch S2 the circuit can be set toclear or extinguish lights from the board, while a manipulation of theswitch 81 provides a ring-back signal to the premises being monitoredindicating the integrity of the circuit.

When the green light is energized, it is to be understood that a currentof .8 to 1.15 ma is flowing through the hard lines 18 and the monitoringcircuit 14. A current of this level causes a suitable voltage to beapplied to the base of the transistor 74 causing this transistor to berendered conductive so that, in effect, transistor 74 is caused tocconduct with a resulting conductive state being imposed on thetransistor causing the lamp 46 to be energized.

In the event the switch 24 is manipulated for establishing a day mode onthe monitoring circuit 14 an increase in the current flow through thehard lines and the circuit 14 is experienced, whereupon the transistor74 of the pick-off circuit of the block F is rendered conductive so thatthe transistor 1 12 is caused to conduct, in response to transistor 104being rendered nonconductive as groundpotential is removed from the basethereof. As the transistor 112 conducts, the lamp 48 is energized forproviding an output of light, white in color. As a practical matter, itis desirable to maintain the lamp 46 in a de-energized condition.Accordingly, the PNP transistor 115, normally maintained in a reversebias state, is provided with its collector being connected to the base.of the NPN transistor 92 while the emitter thereof is connected toground potential, as aforedescribed. The base of the PNP transistor 115,while being connected to ground,'also is connected between the collectorof the transistor 112 and the lamp 48 so that as a current flow throughthe lamp 48 is established the biasing voltage applied to the base ofthe transistor 115 is removed, causing the transistor to conduct forapplying a reverse biasing voltage, at ground potential, to the base ofthe transistor 92. Therefore, it can be appreciated that so long as thelamp 48 is energized, the lamp 46 is biased to its off condition.

In the event the circuit to ground it interrupted, at the monitoringcircuit 14, the transistor 74 is rendered non-conductive, through aremoval of voltage from the base thereof, while the SCR 82 isresponsively caused to conduct for energizing the yellow lamp 44.

Similarly, in the event the circuit 14 is cross-shorted the increase involtage applied to the base of the tran sistor 74 causes this transistorto conduct to apply a gating signal to the SCR 116, whereupon the SCR1116 is rendered conductive for thus energizing the red lamp 50. Ofcourse, a current flow established through any of the lamps 44 through50 results in a gating signal being applied to the SCR 134 for therebyenergizing the blue lamp 60. As a consequence, a switching signal isapplied to the base of the PNP transistor 336. The intelligence thusprovided at the observation station can now be noted and appropriateactions taken.

The switch S2 is then closed to ground the pole 172 and for removingground potential from the lamps. Thus the switching circuits arepermitted to reset for extinguishing intelligence provided by theradiation from the lamps and the signal generator 156. The switch S2 isthen reset to its normal position for grounding the opposite polethereof, whereby the unit 19 is prepared for a subsequent monitoringoperation.

In view of the foregoing, it should be apparent that the circuit of theinstant invention provides a practical solution to the perplexingproblem of electronically monitoring the integrity of remotely relatedbuildings.

Although the invention has been herein shown and described in what isconceived to be the most practical and preferred embodiment, it isrecognized that departures may be made therefrom within the scope of theinvention, which is not to be limited to the illustrative detailsdisclosed.

Having described our invention, what we claim as new and desire tosecure by Letters Patent is:

l. A system for simultaneously monitoring the integ rity of a buildingfrom a remotely related observation station, comprising:

A. an integrity monitoring circuit, characterized by means impartingthereto a selectively variable resistance of two predetermined values,disposed within a selected building including means for continuouslyconducting therethrough an electrical current at a selected one of twoamperages, each amperage being indicative of normal building integrityand dictated by the resistance of the circuit; and

B. an observation circuit located at an observation station remotelyrelated to said building and connected with said monitoring circuitincluding amperage-monitoring circuit means characterized by acolor-coded lamp responsive to the selected amperage of the currentconducted through the monitoring circuit for providing intelligenceindicative of normal building integrity, and circuit means including aplurality of color-coded lamps responsive to changes in the selectedamperage for selectively energizing said color-coded lamps for therebyproviding intelligence indicative of abnorma] building integrity.

2. A system for simultaneously monitoring the integrity of a pluralityof remotely related buildings from a common observation stationcomprising:

A. a plurality of remotely related monitoring circuits each beingsituated within one of a plurality of remotely related buildings;

B. a plurality of observation circuits located at a common observationstation remotely related to said buildings, each including,

1. a plurality of electrically energizable lamps for propagating lightof mutually distinct colors,

2. a plurality of solid state switching circuits, each beingelectrically connected with one of said lamps, and

3. a plurality of solid state switching devices, each being electricallyconnected with one of said solid state switching circuits and responsiveto an electrical signal at a predetermined voltage applied thereto forswitching the solid state switching circuit connected therewith to aconductive state for electrically energizing the lamp connected with theswitching circuit;

D. a plurality of hard lines connecting said plurality of observationcircuits with said plurality of monitoring circuits, each being adaptedto conduct a current of electrical energy, the amperage of which isdetermined by the integrity of one of said buildings;

E. a plurality of pick-off means, each being connected with one of saidmonitoring circuits and with one of said hard lines for applyingelectrical signals at said predetermined voltage to selected solid stateswitching devices included within said one monitoring circuit inaccordance with the am perage of said current; and

F. selectively operable means for verifying the integrity of saidplurality of hard lines.

3. The system of claim 2 wherein the value of said amperage is minimizedin response to an opening of said monitoring circuit, and is maximizedin response to a cross-shorting of said monitoring circuit.

4. The system of claim 2 wherein each of said solid state switchingdevices is an NPN transistor, the collectors thereof being connectedwith said switching circuits.

5. The system of claim 4 wherein said plurality of lamps are connectedin parallel with respect to each other and each of said pick-off meansincludes a potentiometer connected with one of said NPN transistors in amanner such that the resistor thereof is connected between a hard lineand a source of negative electrical potential and the wiper arm thereofis coupled with the base of the NPN transistor connected therewith.

6. The system of claim 5 wherein said observation circuit furtherincludes an electrically energizable status-change lamp, adapted, whenenergized, to propagate light of a color differing from said mutuallydistinct colors, circuit means connected with each of said switchingcircuits and with said status-change lamp, responsive to each conductivestate imposed on said plurality of switching circuits by said pluralityof switching devices for energizing saaid status-change lamp.

7. The system of claim 6 further comprising an audible signal generatorconnected with said circuit means and responsive to an energizationthereof for generat- 9. in a system for remotely monitoring theintegrity of a selected building indicated by the amperage of a flow ofan electrical current, the improvement comprising:

A. a monitoring circuit situated within a selected building includingcircuit means foor maintaining an electrical current established at aselected amperage in the monitoring circuit, said amperage tance of thecircuit, whereby said indicator lamps are selectively energized toprovide intelligence indicating change in building integrity.

10. The improvement of claim 9 wherein said source of electricalpotential comprises a source of negative beiing dictated by theresistance of the circuit and 15 correspondingly indicative of buildingintegrity; and

B. an observation circuit located at a station remotely related to saidbuilding and connected with said monitoring circuit for continuouslymonitoring the amperage of the flow of electrical current in saidmonitoring circuit, including,

1. a plurality of color-coded, electrically energizable indicator lamps,each being responsive to an electrical current flowing through the lampfor propagating light of a predetermined color,

2. a plurality of solid state switching devices, each being connected inseries between a source of electrical potential and one side of one ofsaid indicator lamps adapted to switch to a conductive state in responseto an electrical switching signal applied thereto for establishing aflow of electrical current through the indicator lamp connectedtherewith, and

3. circuit pick'off means connected with said monitoring circuit andwith said plurality of solid state switching devices for selectivelyapplying electrical switching signals to said solid state switchingdevices in response to changes in the amperage of the electrical currentestablished in said monitoring circuit, in response to changes in theresis- 24 v. electrical energy and said pick-off means includes aplurality of NPN transistors, the emitter of each being connected withsaid source of electrical potential and the collector thereof beingconnected with one of said solid state switching devices, and aplurality of potentiometers, each being connected in series with thebase of one NPN transistor of said plurality of NPN transistors and saidmonitoring circuit.

11. The improvement of claim 9 further comprising:

A. an electrically energizable status-change lamp adapted to respond toan electrical current flowing therethrough for propagating light of apredetermined color;

B. further solid state switching means connected in series with saidsource of electrical potential and said status-change lamp adapted toswitch to a conductive state in response to an electrical signal appliedthereto for establishing a flow of electrical current through thestatus-change lamp;

C. further pick-off means including a circuit connected with eachindicator lamp and said further solid state switching means for applyingan electrical signal to said further solid state switching means inresponse to each flow of electrical current established through saidplurality of indicator lamps for thereby establishing a flow ofelectrical current through said status-change lamp whereby saidstatus-change lamp is energized concurrently with the energization ofeach indicator lamp; and

D. circuit means connected with said status-change lamp for maintainingsaid flow of electrical current through the status-change lamp forperiods of determinable durations.

1. A system for simultaneously monitoring the integrity of a buildingfrom a remotely related observation station, comprising: A. an integritymonitoring circuit, characterized by means imparting thereto aselectively variable resistance of two predetermined values, disposedwithin a selected building including means for continuously conductingtherethrough an electrical current at a selected one of two amperages,each amperage being indicative of normal building integrity and dictatedby the resistance of the circuit; and B. an observation circuit locatedat an observation station remotely related to said building andconnected with said monitoring circuit including amperage-monitoringcircuit means characterized by a color-coded lamp responsive to theselected amperage of the current conducted through the monitoringcircuit for providing intelligence indicative of normal buildingintegrity, and circuit means including a plurality of color-coded lampsresponsive to changes in the selected amperage for selectivelyenergizing said color-coded lamps for thereby providing intelligenceindicative of abnormal building integrity.
 2. a plurality of solid stateswitching devices, each being connected in series between a source ofelectrical potential and one side of one of sAid indicator lamps adaptedto switch to a conductive state in response to an electrical switchingsignal applied thereto for establishing a flow of electrical currentthrough the indicator lamp connected therewith, and
 2. a plurality ofsolid state switching circuits, each being electrically connected withone of said lamps, and
 2. A system for simultaneously monitoring theintegrity of a plurality of remotely related buildings from a commonobservation station comprising: A. a plurality of remotely relatedmonitoring circuits each being situated within one of a plurality ofremotely related buildings; B. a plurality of observation circuitslocated at a common observation station remotely related to saidbuildings, each including,
 3. The system of claim 2 wherein the value ofsaid amperage is minimized in response to an opening of said monitoringcircuit, and is maximized in response to a cross-shorting of saidmonitoring circuit.
 3. a plurality of solid state switching devices,each being electrically connected with one of said solid state switchingcircuits and responsive to an electrical signal at a predeterminedvoltage applied thereto for switching the solid state switching circuitconnected therewith to a conductive state for electrically energizingthe lamp connected with the switching circuit; D. a plurality of hardlines connecting said plurality of observation circuits with saidplurality of monitoring circuits, each being adapted to conduct acurrent of electrical energy, the amperage of which is determined by theintegrity of one of said buildings; E. a plurality of pick-off means,each being connected with one of said monitoring circuits and with oneof said hard lines for applying electrical signals at said predeterminedvoltage to selected solid state switching devices included within saidone monitoring circuit in accordance with the amperage of said current;and F. selectively operable means for verifying the integrity of saidplurality of hard lines.
 3. circuit pick-off means connected with saidmonitoring circuit and with said plurality of solid state switchingdevices for selectively applying electrical switching signals to saidsolid state switching devices in response to changes in the amperage ofthe electrical current established in said monitoring circuit, inresponse to changes in the resistance of the circuit, whereby saidindicator lamps are selectively energized to provide intelligenceindicating change in building integrity.
 4. The system of claim 2wherein each of said solid state switching devices is an NPN transistor,the collectors thereof being connected with said switching circuits. 5.The system of claim 4 wherein said plurality of lamps are connected inparallel with respect to each other and each of said pick-off meansincludes a potentiometer connected with one of said NPN transistors in amanner such that the resistor thereof is connected between a hard lineand a source of negative electrical potential and the wiper arm thereofis coupled with the base of the NPN transistor connected therewith. 6.The system of claim 5 wherein said observation circuit further includesan electrically energizable status-change lamp, adapted, when energized,to propagate light of a color differing from said mutually distinctcolors, circuit means connected with each of said switching circuits andwith said status-change lamp, responsive to each conductive stateimposed on said plurality of switching circuits by said plurality ofswitching devices for energizing saaid status-change lamp.
 7. The systemof claim 6 further comprising an audible signal generator connected withsaid circuit means and responsive to an energization thereof forgenerating an audible signal concurrently with the energization of saidstatus-change lamp.
 8. The system of claim 7 further comprisingselectively operable means for simultaneously de-energizing said lampsand terminating the generation of said audible signal.
 9. In a systemfor remotely monitoring the integrity of a selected building indicatedby the amperage of a flow of an electrical current, the improvementcomprising: A. a monitoring circuit situated within a selected buildingincluding circuit means foor maintaining an electrical currentestablished at a selected amperage in the monitoring circuit, saidamperage beiing dictated by the resistance of the circuit andcorrespondingly indicative of building integrity; and B. an observationcircuit located at a station remotely related to said building andconnected with said monitoring circuit for continuously monitoring theamperage of the flow of electrical current in said monitoring circuit,including,
 10. The improvement of claim 9 wherein said source ofelectrical potential comprises a source of negative 24 v. D.C.electrical energy and said pick-off means includes a plurality of NPNtransistors, the emitter of each being connected with said source ofelectrical potential and the collector thereof being connected with oneof said solid state switching devices, and a plurality ofpotentiometers, each being connected in series with the base of one NPNtransistor of said plurality of NPN transistors and said monitoringcircuit.
 11. The improvement of claim 9 further comprising: A. anelectrically energizable status-change lamp adapted to respond to anelectrical current flowing therethrough for propagating light of apredetermined color; B. further solid state switching means connected inseries with said source of electrical potential and said status-changelamp adapted to switch to a conductive state in response to anelectrical signal applied thereto for establishing a flow of electricalcurrent through the status-change lamp; C. further pick-off meansincluding a circuit connected with each indicator lamp and said furthersolid state switching means for applying an electrical signal to saidfurther solid state switching means in response to each flow ofelectrical current established through said plurality of indicator lampsfor thereby establishing a flow of electrical current through saidstatus-change lamp whereby said status-change lamp is energizedconcurrently with the energization of each indicator lamp; and D.circuit means connected with said status-change lamp for maintainingsaid flow of electrical current through the status-change lamp forperiods of determinable durations.